This invention relates to no-return-mark turning, boring or facing tools which are used in conjunction with turning equipment, and more particularly to a method of preventing chips created during the operation of the tool from lodging between the moving parts of such a tool.
A smooth finished surface is needed for components in many mechanisms, for example, discs for automobile brakes. Prior to the advent of no-return-mark tools, the facing of a disc required adjusting the tool to the proper depth of cut before the disc was machined and, after completion of the cutting stroke, laterally moving the cutting edge off the finished surface so that the tool, as it was withdrawn, did not cut a return mark into the otherwise smooth surface.
The no-return-mark tool arose from the desire to eliminate, particularly in high output repetitive manufacturing processes, additional lateral motion of the cutting tools in order to prevent leaving a return mark on the finished surface of the machined piece when the cutting tool is withdrawn. Typically, a no-return-mark tool has a spring-loaded, pivoting cutting edge. As the cutting tool is fed into the work, the cutting pressure overcomes the spring force and allows the cutting edge to pivot and bottom-out against a hardened surface on the tool holder, the cutting edge remaining in this position as long as it is engaged in the cut. As the withdrawal stroke starts the cutting pressure is removed and the spring force pivots the cutting edge away from the finished surface. The tool can thus be withdrawn, leaving no return mark on the finished surface, without lateral movement of the tool setting.
The utility of no-return-mark tools is limited, however, because it is common for chips or metal fragments to become lodged between the moving parts of the tool, preventing the cutting tool from properly pivoting between its cutting and return settings.
It is the object of this invention to provide a no-return-mark tool with a means of preventing chips and other debris from lodging between the moving parts of the tool.